Spam

I tried to find which version I am using (an old one) but don’t know where to look for specs.
My site is custom with a privately designed theme.

My host keeps encouraging me to update but my designer cautioned against it as it may alter the theme.

Is there a spam plugin I can safely use?
I am getting thousands of spam emails via a gmail bot.

I inserted a new plugin for the comments and that has decreased the spam but it is still coming in torrents via email.

Any suggestions?